ddanielr commented on PR #4596:
URL: https://github.com/apache/accumulo/pull/4596#issuecomment-2127560868
> > I'm open to suggestions on how to best proceed with this change.
>
> We could attempt the following :
>
> * Create a new prefix for the new data format, maybe `~scanr`
> * In 2.1.3 servers would start writing the new format under the new prefix
> * Push all of the logic for encoding/decoding to/from key/value into
ScanServerRefTabletFile
> * Make ScanServerRefTabletFile internally track the prefix it was decoded
from and it can use that to create mutations
> * When scanning to gather ScanServerRefTabletFile, scan both prefixes
>
> Pushing all of the encode/decode into ScanServerRefTabletFile seens like a
nice general improvement on its own because it would bring that logic all to a
single place in the code. Might look something like the following. Then except
for having to scan both prefixes, most of the code dealing w/
ScanServerRefTabletFile would hopefully be oblivious to how the data is
represented.
>
> ```java
> public class ScanServerRefTabletFile extends TabletFile {
>
> private String prefix; // either old prefix of ~sserv or new one of
~scanr
> private Text uuid;
> private Text serverAddress;
>
> public ScanServerRefTabletFile(String file, String serverAddress, UUID
serverLockUUID) {
> super(new Path(URI.create(file)));
> // for new data always use the new prefix
> prefix = "~scanr";
> uuid = new Text(serverLockUUID.toString());
> this.serverAddress = new Text(serverAddress);
> }
>
> private boolean isOldPrefix(Key k){
> return k.getRow().toString().startsWith("~sserv");
> }
>
> private static String extractFile(Key k) {
> // TODO extract file from key depending on prefix
> }
>
> public ScanServerRefTabletFile(Key k, Value v) {
> super(new Path(URI.create(extractFile(k))));
> // TODO use prefix to determine how to extract uuid and serverAddress
from key/value
> }
>
> public void put(Mutation m) {
> // TODO use prefix determine how to put uuid, server, and file into
the mutation
> }
>
> public void putDelete(Mutation m) {
> // TODO use prefix determine how to put delete for uuid, server, and
file into the mutation
> }
> }
> ```
That makes a lot of sense and is much cleaner than dealing with the change
in ample.
The existing code doesn't matter since the range is different and on the
switch to 3.x we just remove the old range.
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